1. Field of the Invention
The present invention relates to electroacoustic transducers used in hearing aids, for example.
2. Related Background Art
An known example of this kind of electroacoustic transducer is found in Japanese Unexamined Patent Publication No. 58-99099. An electroacoustic transducer disclosed in this Patent Publication comprises a case serving as a housing and a drive unit accommodated in the case. The drive unit includes a plate member, a coil, a pair of magnets and a yoke. The plate member includes a base plate portion, side plate portions extending parallel to each other from two opposite ends of the base plate portion, and an armature extending between the side plate portions from a central part of the base plate portion. The coil is bonded to inner surfaces of the side plate portions of the plate member. The two magnets are individually fixed to opposed inner surfaces of the yoke. Two opposite side surfaces of the yoke are fixed to extreme parts of the inner surfaces of the side plate portions of the plate member. With the plate member and the yoke fixed together, a terminal end of the armature is inserted in between the magnets such that the armature does not come into contact with the magnet pair. The drive unit is fixed to the case as the bottom surface of the yoke is fixed to the bottom of the case.
Both ends of the coil are passed through holes made in the case and connected to signal input terminals of a terminal strip which is fixed to a side wall of the case. In the electroacoustic transducer of the above-described type, conductor used for forming the coil is usually an extremely thin copper wire measuring about 25 xcexcm in diameter.
The conventional electroacoustic transducer of the aforementioned construction has such disadvantages as (1) handling of end portions of the conductor is difficult since the conductor is extremely thin; and (2) the end portions of the conductor are liable to break when they are connected to the signal input terminals of the terminal strip because the terminal strip is fixed to the case. Thus, one of major problems of the conventional electroacoustic transducer is that it is impossible to easily connect the end portions of the conductor to the terminal strip.
Another problem of the conventional electroacoustic transducer is that lead wires from the coil to the signal input terminals of the terminal strip are liable to break due to vibrations or other external impact to the transducer, such as its dropping. This is because the distance between the coil and the terminal strip is long in the conventional electroacoustic transducer.
The present invention has been made in view of the aforementioned problems of the prior art. Accordingly, it is an object of the invention to provide an electroacoustic transducer which makes it possible to easily connect lead wire portions of a coil to signal input terminals and reduce the risk of lead wire breakage.
In one aspect of the invention, an electroacoustic transducer comprises a coil formed by winding a conductor and a bobbin unit on which the coil is formed, wherein the bobbin unit includes signal input terminals and coil side terminals to which the ends of the conductor are fixed, the coil side terminals being electrically connected to the signal input terminals, and wherein the signal input terminals and the coil side terminals are provided individually at different end portions of the bobbin unit.
Since the signal input terminals and the coil side terminals are provided on the bobbin unit in this electroacoustic transducer of the invention, the conductor is electrically connected to the signal input terminals when the ends of the conductor are fixed to the coil side terminals. This arrangement facilitates connection of the ends of the conductor constituting the coil to the signal input terminals. Furthermore, since the coil side terminals are provided on the bobbin unit and the coil is formed on the bobbin unit, it is possible to shorten the length of lead wire portions between the coil and the coil side terminals and thereby prevent breakage of the conductor between the coil and the coil side terminals.
Moreover, since the signal input terminals and the coil side terminals are provided at the different end portions of the bobbin unit in the electroacoustic transducer of the invention, the signal input terminals and the coil side terminals are separated from each other. Therefore, the distance from the tip of a welding electrode to each signal input terminal becomes larger than the distance from the tip of the electrode to the corresponding coil side terminal when the ends of the conductor are connected to the coil side terminals by arc welding, for instance. This helps prevent the occurrence of an arc between the tip of the electrode and the signal input terminals and produce an arc between the tip of the electrode and the coil side terminals in a reliable fashion. All these features of the invention ensure reliable connection of the ends of the conductor to the coil side terminals when fixing the ends of the conductor to the coil side terminals by arc welding.
In one preferred form of the invention, the electroacoustic transducer further comprises an armature unit having a base plate portion, at least one side plate portion extending from the base plate portion, and an armature extending from the base plate portion in the same direction as the side plate portion, the bobbin unit further including a base portion in which a hole for inserting the armature of the armature unit is made, a coil winding portion on which the conductor is wound, a magnet positioning portion for positioning a magnet, and a magnet retainer for retaining the magnet which is positioned in the magnet positioning portion, wherein the signal input terminals and the coil side terminals are provided at opposite positions with the hole in the base portion located in between. This construction makes it easy to arrange the signal input terminals and the coil side terminals on the base portion of the bobbin unit in which the hole for inserting the armature of the armature unit is made.
Furthermore, since the signal input terminals and the coil side terminals are provided on opposite positions with the hole in the base portion located in between, the signal input terminals and the coil side terminals are separated from each other. Therefore, the distance from the tip of a welding electrode to each signal input terminal becomes larger than the distance from the tip of the electrode to the corresponding coil side terminal when the ends of the conductor are connected to the coil side terminals by arc welding, for instance. This helps prevent the occurrence of an arc between the tip of the electrode and the signal input terminals and produce an arc between the tip of the electrode and the coil side terminals in a reliable fashion. All these features of the invention ensure reliable connection of the ends of the conductor to the coil side terminals when fixing the ends of the conductor to the coil side terminals by arc welding.
In another preferred form of the invention, the armature unit is fixed to the bobbin unit by fixing the side plate portion to the magnet retainer, and there is formed a clearance between the base portion in the bobbin unit and the base plate portion of the armature unit when the armature unit is fixed to the bobbin unit. This construction prevents direct contact between the side plate portion of the armature unit and the base portion of the bobbin unit and thereby prohibits the base portion of the bobbin unit from adversely affecting vibrations of the armature.
In still another preferred form of the invention, the base portion, the coil winding portion and the magnet positioning portion are one-piece molded using a resin material. This makes it possible to reduce the number of components and facilitate winding of the conductor on the bobbin unit and its assembly including fixing of the magnet.
In yet another preferred form of the invention, the electroacoustic transducer further comprises a housing in which the bobbin unit is accommodated, wherein an opening is formed in the housing at its location corresponding to the signal input terminals, and the signal input terminals project to the exterior of the housing through the opening when the bobbin unit is accommodated in the housing. With this arrangement, it becomes possible to provide a construction in which the signal input terminals are exposed to the exterior of the housing in a simple and inexpensive way.
In another aspect of the invention, an electroacoustic transducer comprises a coil formed by winding a conductor and a bobbin unit on which the coil is formed, wherein the bobbin unit includes signal input terminals and coil side terminals to which the ends of the conductor are fixed, the coil side terminals being electrically connected to the signal input terminals, wherein the ends of the conductor are fixed to the coil side terminals by arc welding, and wherein the signal input terminals and the coil side terminals are provided at positions where the distance from the tip of an electrode used for arc welding to the coil side terminals is smaller than the distance from the tip of the welding electrode to the signal input terminals.
Since the signal input terminals and the coil side terminals are provided on the bobbin unit in this electroacoustic transducer of the invention, the conductor is electrically connected to the signal input terminals when the ends of the conductor are fixed to the coil side terminals. This arrangement facilitates connection of the ends of the conductor constituting the coil to the signal input terminals. Furthermore, since the coil side terminals are provided on the bobbin unit and the coil is formed on the bobbin unit, it is possible to shorten the length of lead wire portions between the coil and the coil side terminals and thereby prevent breakage of the conductor between the coil and the coil side terminals.
In this electroacoustic transducer of the invention, the distance from the tip of the welding electrode to each signal input terminal becomes larger than the distance from the tip of the electrode to the corresponding coil side terminal in arc welding. This helps prevent the occurrence of an arc between the tip of the electrode and the signal input terminals and produce an arc between the tip of the electrode and the coil side terminals in a reliable fashion. All these features of the invention ensure reliable connection of the ends of the conductor to the coil side terminals by arc welding.
In one preferred form of the invention, the electroacoustic transducer further comprises a housing in which the bobbin unit is accommodated, wherein an opening is formed in the housing at its location corresponding to the signal input terminals, and the signal input terminals project to the exterior of the housing through the opening when the bobbin unit is accommodated in the housing. With this arrangement, it becomes possible to provide a construction in which the signal input terminals are exposed to the exterior of the housing in a simple and inexpensive way.
In still another aspect of the invention, an electroacoustic transducer comprises a coil formed by winding a conductor, a bobbin unit on which the coil is formed, and a housing in which the bobbin unit is accommodated, wherein the bobbin unit includes signal input terminals and coil side terminals to which the ends of the conductor are fixed, the coil side terminals being electrically connected to the signal input terminals, and wherein an opening is formed in the housing at its location corresponding to the signal input terminals, and the signal input terminals project to the exterior of the housing through the opening when the bobbin unit is accommodated in the housing.
Since the signal input terminals and the coil side terminals are provided on the bobbin unit in this electroacoustic transducer of the invention, the conductor is electrically connected to the signal input terminals when the ends of the conductor are fixed to the coil side terminals. This arrangement facilitates connection of the ends of the conductor constituting the coil to the signal input terminals. Furthermore, since the coil side terminals are provided on the bobbin unit and the coil is formed on the bobbin unit, it is possible to shorten the length of lead wire portions between the coil and the coil side terminals and thereby prevent breakage of the conductor between the coil and the coil side terminals.
Furthermore, since the signal input terminals project to the exterior of the housing through the opening when the bobbin unit is accommodated in the housing in this electroacoustic transducer of the invention, it is possible to provide a construction in which the signal input terminals are exposed to the exterior of the housing in a simple and inexpensive way.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.